Radiation therapy for Wilms tumour

Radiation therapy uses high-energy rays or particles to destroy cancer cells. It is sometimes used to treat children with Wilms tumour that is more advanced or has unfavourable (anaplastic) histology. Radiation may be given to the abdomen or chest or other sites of metastasis. Children with stage I and stage II Wilms tumours with favourable histology do not receive radiation therapy. The healthcare team will consider your child’s personal needs to plan the type and amount of radiation, and when and how it is given. Your child may also receive other treatments.

Depending on the spread of the tumour, radiation therapy may be given to just the kidney area or to the entire abdomen. Your child may have radiation to the abdomen to:

destroy cancer cells left behind after surgery and chemotherapy and reduce the risk of the cancer recurring (called adjuvant radiation therapy)

treat advanced cancer

shrink a tumour before surgery so the surgeon can try to remove it (called neoadjuvant radiation therapy)

Radiation therapy may be given to the chest to treat Wilms tumour that has spread, or metastasized, to the lung.

The following are the types of radiation therapy most commonly used to treat Wilms tumour.

External beam radiation therapy

During external beam radiation therapy, a machine directs radiation through the skin to the tumour and some of the tissue around it. The radiation therapy team will base the size of the treatment area on the amount of cancer present. Very young children may be sedated before radiation therapy to keep them still during treatment.

Radiation therapy is given to the abdomen as soon as possible after surgery to remove the tumour. Doctors base when to given radiation on the histology of the tumour. Radiation therapy is given within:

14 days of surgery to remove Wilms tumour with favourable histology

10 days of surgery to remove Wilms tumour with unfavourable (anaplastic) histology

Modern radiation techniques allow doctors to target the area to be treated much more accurately, while sparing as much surrounding normal tissue as possible.

3-dimensional conformal radiation therapy (3D-CRT)

In 3D-CRT, the radiation oncologist uses MRI images to map the exact location and shape of the tumour. Several radiation beams are then shaped and aimed at the tumour from different directions to treat the tumour from all angles. Each individual beam is fairly weak and less likely to damage normal tissues. A higher dose of radiation is delivered where the beams converge at the tumour.

Intensity-modulated radiation therapy (IMRT)

IMRT is similar to 3D-CRT in that it delivers radiation from many different angles to treat the entire tumour. In addition to shaping and aiming the radiation beams, IMRT allows the radiation oncologist to adjust the strength, or intensity, of the individual beams. This allows a higher dose to be delivered to the tumour and reduces the dose of radiation reaching nearby normal tissues.